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1.
《应用海洋学学报》2014,(2)
反硝化与厌氧氨氧化作用是海洋结合态氮迁出的主要途径,15N示踪法是定量反硝化和厌氧氨氧化作用的新方法,它具有灵敏度高、可同步测量反硝化与厌氧氨氧化速率的优点.本研究开展了一系列方法学实验,以确定高纯氦气驱赶水样所含气体的时间、超声赶气时间、同位素比值质谱仪测量N2含量的精度、N2含量及其同位素组成测定的工作曲线以及示踪剂的最佳添加量等,从而确立起15N示踪同步测定海水反硝化和厌氧氨氧化速率的方法.所建立方法测量N2含量的相对标准偏差小于8%,可满足海洋反硝化与厌氧氨氧化速率测定的需要.应用该方法实测了厦门筼筜湖富氧与缺氧水体的反硝化与厌氧氨氧化速率,结果表明,缺氧底层水的反硝化速率[4.10~5.47μmol/(dm3·d)]比富氧表层水[0.43~0.46μmol/(dm3·d)]明显来得高,但缺氧底层水的厌氧氨氧化速率[0.00~0.12μmol/(dm3·d)]则比富氧表层水的速率[0.52~0.67μmol/(dm3·d)]低得多. 相似文献
2.
反硝化与厌氧氨氧化作用是海洋结合态氮迁出的主要途径,15N示踪法是定量反硝化和厌氧氨氧化作用的新方法,它具有灵敏度高、可同步测量反硝化与厌氧氨氧化速率的优点.本研究开展了一系列方法学实验,以确定高纯氦气驱赶水样所含气体的时间、超声赶气时间、同位素比值质谱仪测量N2含量的精度、N2含量及其同位素组成测定的工作曲线以及示踪剂的最佳添加量等,从而确立起15N示踪同步测定海水反硝化和厌氧氨氧化速率的方法.所建立方法测量N2含量的相对标准偏差小于8%,可满足海洋反硝化与厌氧氨氧化速率测定的需要.应用该方法实测了厦门筼筜湖富氧与缺氧水体的反硝化与厌氧氨氧化速率,结果表明,缺氧底层水的反硝化速率[4.10～5.47μmol/（dm3·d）]比富氧表层水[0.43～0.46μmol/（dm3·d）]明显来得高,但缺氧底层水的厌氧氨氧化速率[0.00～0.12μmol/（dm3·d）]则比富氧表层水的速率[0.52～0.67μmol/（dm3·d）]低得多. 相似文献
3.
生物固氮作用是一个重要的海洋新氮来源,在海洋生物地球化学循环中扮演着不可替代的角色。基于稳定同位素（15N2）示踪吸收法,是目前直接测定海洋生物固氮速率最有效的手段。其中,高效、洁净地将15N2引入海水培养体系,并准确定量培养体系底物的同位素示踪水平,是同位素示踪吸收法准确获取固氮速率的关键。本研究针对15N2同位素示踪剂引入这一关键环节进行了探讨,确认改进气泡法是将15N2引入海水培养体系的首选操作。在对培养体系造成的较小扰动的情况下,可将培养体系氮气底物的15N原子丰度提升至10%以上,相对于另一种导入同位素示踪剂的手段——预溶解海水法,改进气泡法将培养瓶中氮气底物的15N原子丰度提升了近200%。此外,改进气泡法还具有最小化痕量金属沾污、操作简便等优点。将改进气泡法结合与稳定同位素比值质谱测定结合,是准确测定水体生物固氮速率的推荐方法。 相似文献
4.
沉积物中的异化硝酸盐还原过程对于海洋氮循环起着至关重要的作用。基于15N标记的培养技术是目前测定沉积物异化硝酸盐还原的主要手段。准确快速测定15N标记的产物(29N2、 30N2)是量化异化硝酸盐还原各个过程速率的关键。本研究自行组装膜进样质谱系统用于29N2和30N2的测定,对其测量条件进行了优化。结果表明,进样蠕动泵进样流速0.80 mL/min,进样时间3~3.5 min,恒温槽温度20~25℃,同时铜还原炉温度在300~600℃的条件下,^29N2/^28N2和^30N2/^28N2的测试精密度分别可以控制在0.1%和1%以内,比较适合29N2和30N2的测定。利用自组装的膜进样质谱系统结合15N标记的培养技术研究了青岛石老人沙滩沉积物中的异化硝酸盐还原过程。石老人沙滩沉积物不存在将硝酸盐完全还原为氮气好氧的反硝化。厌氧铵氧化、厌氧反硝化和异化硝酸盐还原为铵(Dissimilatory Nitrate Reduction to Ammonium,DNRA)的潜在速率(以湿沉积物N计)分别为(0.05±0.01) nmol/(cm^3·h),(2.32±0.21) nmol/(cm^3·h)和(1.02±0.15) nmol/(cm^3·h)。厌氧反硝化是硝酸盐异化还原主要的贡献者,其比例接近70%,其次是DNRA,比例可达30%,而厌氧铵氧化的贡献最低,仅为1%。在N2产生过程中,主要贡献者是反硝化,厌氧铵氧化的贡献仅为2%。 相似文献
5.
采用N2通量法,在一套连续流动培养装置中测定珠江口淇澳岛海岸带的反硝化速率,探讨各种因素对淇澳岛海岸带反硝化速率的影响.结果表明,反硝化速率受NO3-的利用率影响,而不是NO3-的绝对浓度.大型红树植物对淇澳岛海岸带的反硝化速率影响最大,其次是硝酸盐利用率,而有机质含量的影响较小.由于大型红树植物的影响,样品Q0411-5的反硝化速率比同在岛内的Q0411-3高出1倍.样品Q0412-14的NO3-培养前后的浓度变化(△NO3-)是Q0412-9的4倍多,因为受硝酸盐利用率的影响,它的反硝化速率却是Q0412-9的2倍多.温度对反硝化速率的影响程度尚不能确定. 相似文献
6.
本文研究碳氮(C/N)比变化对移动床生物膜反应器(MBBR)处理海水养殖废水性能的影响。结果表明,当C/N比从7∶1降至3∶1,出水COD浓度无明显变化,平均去除率保持在90%以上。C/N比的变化对脱氮过程有较大影响,当C/N比从7∶1降低至3∶1,NH+4-N去除率由89.51%±1.24%增至92.70%±1.08%,NO-2-N浓度由(4.84±0.50)mg/L降至0 mg/L,NO-3-N浓度由(0.47±0.29)mg/L升至(8.12±0.25)mg/L。C/N比的降低提高了比氨氧化速率、比亚硝酸盐氧化速率和与硝化相关的微生物酶活性,但降低了比耗氧速率、比硝酸盐还原速率、比亚硝酸盐还原速率、脱氢酶活性和与反硝化相关的微生物酶活性。松散型胞外聚合物和紧密型胞外聚合物的多糖含量随C/N比的降低而降低,说明在低COD条件下,多糖能够被微生物利用。微生物群落的丰富度和多样性随C/N比的降低而降低,硝化菌属(Nitrosomonas和Nitrospira)和反硝化菌属(Azoarcus、Comamonas、Hyphomicrobium、Paracoccus、Thauera、Devosia、Pseudomonas和Rhodanobacter)的相对丰度发生改变,从而影响MBBR脱氮性能。 相似文献
7.
分离自对虾养殖池塘的地衣芽孢杆菌(Bacillus licheniformis)MP15具有高效的异养硝化-好氧反硝化性能。为了进一步研究菌株MP15的脱氮特性和脱氮机制,本研究采用氮同位素标记法,对其在氮基础降解液中的脱氮特性和机制进行了深入的研究。研究结果显示:在初始无机氮浓度为42 mg/L的氮基础降解液中,其对NH~+_4-N、NO~-_2-N和NO~-_3-N的最大去除速率分别为1.03 mg NH~+_4-N/(L·h)、1.74 mg NO~-_2-N/(L·h)和1.02 mg NO~-_3-N/(L·h)。氮代谢过程中羟胺氧化还原酶、亚硝酸盐还原酶和硝酸盐还原酶的酶比活力分别为0.540 6、0.157 8和0.160 9 U/mg。对菌株MP15脱氮过程中的~(15)N同位素示踪结果显示,以NH~+_4-N作为唯一氮源时,仅产生~(15)N_2O;当菌株MP15分别以NO~-_2-N和NO~-_3-N作为唯一氮源时,可同时检测到~(15)N_2O和~(15)N_2。综合上述结果,菌株MP15对无机氮的去除主要包括:同化作用、硝化作用和反硝化作用。其中对NH~+_4-N的硝化途径为:NH~+_4-N→NH_2OH→N_2O;对NO~-_2-N的硝化-反硝化途径为:NO~-_3-N←NO~-_2-N→N_2O/N_2;其对NO~-_3-N的反硝化途径为:NO~-_3-N→NO~-_2-N→N_2O/N_2。 相似文献
8.
9.
针对海水闭合循环养殖系统废水脱氮过程中低C/N的问题,采用室内试验装置,研究了以可生物降解聚合物材料(BDPs)PBS为碳源和生物膜载体的填料床反应器对含盐水体中硝酸盐的去除效果及其影响因素。结果表明,反应器能有效去除含盐水体中的硝酸盐,出水DOC浓度小,出水pH值随反硝化反应的进行有上升的趋势。温度和水力停留时间对反应器的脱氮效率影响较大,在温度为14~30℃范围内,温度为30℃时的反硝化速率比14℃时的2倍还要大,反硝化温度常数为0.039;水力停留时间对NO3?-N去除率起重要作用,NO3?-N去除率随水力停留时间的延长而提高。进水NO3?-N浓度对反应器的处理效率有一定影响,浓度过高会导致NO3?-N去除率下降。反应器对进水pH值和DO冲击负荷的适应能力很强,当进水pH值在5.0~9.0与进水DO在2.1~6.8 mg/L范围内变化时,反应器的NO3?-N去除率基本没有变化。 相似文献
10.
2004年1、4、8、10月在大亚湾海域的4个站点采用自行设计和制作的无扰动沉积物采样器采集沉积物样品,通过使用AIT技术(乙炔同时抑制硝化与反硝化作用),进行实验室同步恒温受控模拟培养实验,并同时测定沉积物上覆水的温度、盐度、DO和pH值,沉积物的Eh值和有机质含量,间隙水的NO3-、NO2-和NH4 浓度,研究沉积物中的硝化与反硝化速率及其影响因素。结果显示大亚湾沉积物的硝化速率范围为[(0.00—4.68)±0.87]μmol/(m2·h);反硝化速率范围[(0.00—2.88)±0.41]μmol/(m2·h);硝化与反硝化作用之间存在耦合,比例范围为0%—100%。沉积物的硝化、反硝化速率和耦合比例与上覆水的温度、DO含量,及沉积物中的有机质含量和Eh值密切相关,人类活动对沉积物的硝化与反硝化作用有明显的影响。 相似文献
11.
海洋中的氮循环是海洋生物地球化学研究的热点领域之一,而硝化过程是氮循环的关键一环,准确获取硝化速率对于丰富海洋氮循环的认识至关重要。15N标记同位素技术是目前国际上最为广泛使用的硝化速率测定方法,该方法的核心在于准确测定15N加富样品产生的15NO2-和15NO3-的含量,但目前的方法普遍存在测试时间较长、测试成本较高、所需样品体积较大或者检测限较高等问题。研究以低成本的膜进样质谱作为15N加富样品测试设备,建立了基于镉柱与氨基磺酸双还原体系测定15N加富样品中15NO3-含量的方法。经条件优化实验确定的具体方法:采用1 mol/L HCl配制15 mmol/L的氨基磺酸（SA）作为反应试剂除去样品原有的NO2-,然后利用镉柱将15NO 相似文献
12.
The mechanisms regulating N2O production in an estuarine sediment (Tama Estuary, Japan) were studied by comparing the change in N2O production with those in nitrification and denitrification using an experimental continuous-flow sediment–water system with15N tracer (15N-NO−3 addition). From Feburary to May, both nitrification and denitrification in the sediment increased (246 to 716 μmol N m−2 h−1and 214 to 1260 μmol N m−2 h−1, respectively), while benthic N2O evolution decreased slightly (1560 to 1250 nmol N m−2 h−1). Apparent diffusion coefficients of inorganic nitrogen compounds and O2at the sediment–water interface, calculated from the respective concentration gradients and benthic fluxes, were close to the molecular diffusion coefficients (0·68–2·0 times) in February. However, they increased to 8·8–52 times in May except for that of NO−2, suggesting that the enhanced NO−3 and O2supply from the overlying water by benthic irrigation likely stimulated nitrification and denitrification. Since the progress of anoxic condition by the rise of temperature from February to May (9 to 16 °C) presumably accelerated N2O production through nitrification, the observed decrease in sedimentary N2O production seems to be attributed to the decrease in N2O production/occurrence of its consumption by denitrification. In addition to the activities of both nitrification and denitrification, the change in N2O metabolism during denitrification by the balance between total demand of the electron acceptor and supply of NO−3+NO−2 can be an important factor regulating N2O production in nearshore sediments. 相似文献
13.
T. Yoshinari M. A. Altabet S. W. A. Naqvi L. Codispoti A. Jayakumar M. Kuhland A. Devol 《Marine Chemistry》1997,56(3-4)
Nitrous oxide (N2O) is a trace gas that is increasing in the atmosphere. It contributes to the greenhouse effect and influences the global ozone distribution. Recent reports suggest that regions such as the Arabian Sea may be significant sources of atmospheric N2O.In the ocean, N2O is formed as a by-product of nitrification and as an intermediary of denitrification. In the latter process, N2O can be further reduced to N2. These processes, which operate on different source pools and have different magnitudes of isotopic fractionation, make separate contributions to the 15N and18O isotopic composition of N2O. In the case of nitrification in oxic waters, the isotopic composition of N2O appears to depend mainly on the 15N/14N ratio of NH+4 and the 18O/16O ratio of O2 and H2O. In suboxic waters, denitrification causes progressive 15N and 18O enrichment of N2O as a function of degree of depletion of nitrate and dissolved oxygen. Thus the isotopic signature of N2O should be a useful tool for studying the sources and sinks for N2O in the ocean and its impact on the atmosphere.We have made observations of N2O concentrations and of the dual stable isotopic composition of N2O in the eastern tropical North Pacific (ETNP) and the Arabian Sea. The stable isotopic composition of N2O was determined by a new method that required only 80–100 nmol of N2O per sample analysis. Our observations include determinations across the oxic/suboxic boundaries that occur in the water columns of the ETNP and Arabian Sea. In these suboxic waters, the values of δ15N and δ18O increased linearly with one another and with decreasing N2O concentrations, presumably reflecting the effects of denitrification. Our results suggest that the ocean could be an important source of isotopically enriched N2O to the atmosphere. 相似文献
14.
浒苔对NH+4-N与NO-3-N吸收的相互作用 总被引：1，自引：0，他引：1
在国内首次研究了大型海洋绿潮藻浒苔(Ulva prolifera)对NH4+-N与NO 3--N两种氮源的选择吸收作用。结果表明:当两种氮源等浓度比例存在时,随着NH4+-N与NO3--N浓度升高,藻体对NH4+-N的吸收速率逐渐升高,而对NO3--N吸收受到抑制;当NO3--N和NH 4+-N高浓度比存在时,藻体对NH4-N的吸收速率随着NO3--N/NH4+-N比例的升高和NH4-N浓度的下降而降低;当NO3--N和NH4+-N低浓度比存在时,藻体对NH+4-N保持较高的吸收速率,而对NO3--N的吸收效率随着NO3--N浓度的降低而降低;浒苔具有同时利用水体中较高浓度的NH+4-N和NO3--N的能力,只有当NH4+-N或NO3--N浓度较低时,才以吸收相对应的氮源为主。这说明浒苔能够快速、大量地吸收水体中氮源,为爆发性增殖贮备物质条件。同时,即便两种氮源同时存在,浒苔对NH+4-N的吸收速率也远高于对NO3--N的吸收速率,因此,控制NH4+-N的大量输入仍是预防浒苔绿潮爆发的关键。 相似文献
15.
The loss of added 15N-labelled NH4+ from bottom sediment was studied in situ in a shallow saline Louisiana Gulf Coast lake. 15N-labelled NH4+ was uniformly mixed with sediment at the level of 35 μg N g?1 dry sediment for 24 h before being weighed into polyethylene containers. The 15N-enriched sediment was incubated on the lake bottom for periods up to 337 days. At intervals, triplicate samples were taken and analyzed for inorganic NH4+, organic N, and denitrification rates. Concentrations of NH4+ in the 15NH4+ enriched sediment samples were at levels similar to those measured in vertical intact cores removed from the lake at each sampling date. The initial and final isotopic compositions of NH4+ in the incubated sediments were 44.26 and 0.521 atom % 15N excess, respectively. 15N enrichment in the organic N fraction increased rapidly during the first 15 days of incubation and then increased slowly from 15 to 123 days. Denitrification, estimated by the acetylene blockage technique, ranged from 0.994 to 0.079 ng N g?1 dry sediment per hour. The mean denitrification rate for the 337-day period was 0.28 ng N g?1 h?1. There was no statistical difference in the recovery of 15N between 15 and 337 days of incubation. When the added 15N became incorporated into the organic N pool, little or no further 15N was lost. 相似文献
16.
Understanding phosphorus dynamics in marine environment is of great importance, and appropriate tracers for phosphorus cycling in oceans are invaluable. In this study, two methods were developed for extraction, purification, and determination of naturally occurring 32P and 33P in rainwater, marine plankton and sediments using both a low-level beta counter (LBC) and an ultra-low-level liquid scintillation spectrometer (LSS). Blanks, chemical yields and counting efficiencies were quantified for both methods. The chemical purification of 32P and 33P separated by both procedures was validated by their decay curves. The absorber thickness of aluminum for LBC was assessed as 39.2 mg/cm 2 . 32P and 33P specific activities in some rain samples were determined by both methods and showed good consistent results. The advantage of the LSS over the LBC is apparent in its high counting efficiency and in determining samples with high concentration of stable phosphorus. However, when measuring environmental samples with low concentration of stable phosphorus, such as rainwater, both methods can be used and each has its distinct advantage. 相似文献
17.
Keiji Horikawa Masao Minagawa Yoshihisa Kato Masafumi Murayama Seiya Nagao 《Journal of Oceanography》2006,62(4):427-439
N2 fixation is an important biological process that adds new nitrogen to oceans and plays a key role in modulating the oceanic
nitrate inventory. However, it is not known how, when, and where N2 fixation rates have varied in response to past climate changes. This study presents a new record of nitrogen isotopic composition
(δ15N) over the last 83 kyr from a sediment core (KH02-4 SUP8) taken in the Sulu Sea in the western equatorial Pacific region;
data allow the N2 fixation variability in the sea to be reconstructed. Sediments, sinking, and suspended particulate organic matter (POM) all
have lighter isotopic values compared to the δ15N values of substrate nitrate (av. 5.8‰) in North Pacific Intermediate Water. These lighter δ15N values are regarded as reflecting N2 fixation in the Sulu Sea surface water. A δ15N mass balance model shows that N2 fixation rates were significantly enhanced during 54–34 kyr in MIS-3 and MIS-2. It has been speculated that higher interglacial
denitrification rates in the Arabian Sea and the eastern tropical Pacific would have markedly decreased the global oceanic
N inventory and contributed to the increase in N2 fixation in oligotrophic regions, but such a model was not revealed by our study. It is possible that changes in N2 fixation rates in the Sulu Sea were regional response, and accumulation of phosphate in the surface waters due to enhanced
monsoon-driven mixing is thought to have stimulated enhancements of N2 fixation during MIS-3 and MIS-2. 相似文献
18.
厦门湾水体中颗粒有机碳的垂向输出通量:234Th/238U不平衡的应用 总被引：2，自引：1，他引：2
对厦门湾塔角附近海域某站位叶绿素 a、POC、初级生产力、234Th/238U不平衡进行的周日变化研究表明,POC含量介于14.4～34.6 mmol/m3之间,其中碎屑有机碳与活体有机碳所占份额分别为74%～92%和8%～26%.POC垂直分布呈现由表及底降低的趋势,且白昼期间POC含量高于晚间,说明研究海域POC含量与生物过程具有密切联系.初级生产力水平在1d之中变化达5倍,垂直分布亦随深度增加而降低,与叶绿素a的变化相对应.短时间(2h)培养获得的初级生产力水平明显高于长时间培养(24 h)的结果,证实部分新固定的碳被优先呼吸排出.结合234Th/238U不平衡法获得的颗粒态234Th输出通量及输出界面颗粒物中的POC/PTh比值,可计算出真光层 POC的垂向输出通量为16.0mmol/(m2·d),其中碎屑有机碳与活体有机碳贡献的数量分别为13.3和2.7mmol/(m2·d).POC输出通量与初级生产力的比值(ThE比值)平均为0.31,真光层POC停留时间平均为11d.上述结果与Aksnes和Wassmann[1]的模型计算结果相吻合,但与其他大多数模型的结果仍存在一定的差异. 相似文献
19.
Vertical gas profiles of N2, N2O and O2were obtained in intact sediment cores from a Tagus estuary salt marsh using membrane inlet mass spectrometry. This technique allows direct measurements of dissolved gas concentrations with minimal disturbance. O2concentrations decreased sharply with depth, becoming undetectable below 14mm. Denitrification products (N2and N2O) occurred in the surface layer of the sediment where O2was present. Diffusion of N2and N2O from the anaerobic zone, denitrification in anaerobic microsites and aerobic denitrification are possible explanations for this observation. N2was the sole product of denitrification in control sediment cores probably because of the great demand for electron acceptors in this sediment. The addition of NO3 − and CH3CO2 − increased the concentrations of N2and N2O in the sediment. Significantly higher concentrations in treated cores occurred between 1·5 and 2·0cm for N2and between 0·5 and 1·5cm for N2O. The peak in N2concentration occurred in the anaerobic zone of the sediment, close to the aerobic–anaerobic interface while the peak in N2O concentration occurred above this interface where concentrations of O2were approximately 10μM. This is indicative that, in this sediment, production of N2O is less sensitive to the presence of O2than reduction of N2O to N2. 相似文献